"Firefox will: Never remember history", but still does in "Recently Closed Tabs/Windows"
Why when I set "Firefox will: Never remember history", Firefox still remembers it in "Recently Closed Tabs/Windows"? I don't want to restart my browser. Also, having this setting enabled disables the "Start Private Browsing" feature. Ain't that odd? I could even go as far as accusing Firefox of double standards
Re: "Firefox will: Never remember history", but still does in "Recently Closed Tabs/Windows"
If you set "Firefox will: Never remember history" then you enter Private Browsing mode immediately.
You can see a grayed "Tools > Stop Private Browsing" to confirm that.
This doesn't affect already stored History, but Firefox won't add new visited links to the History.
If you want to remove sites from the History then you need to do that yourself.
You can (temporarily) set the pref browser.sessionstore.max_tabs_undo to 0 to clear the Recently Closed Tabs list.
Use the Reset context menu item to re-enable Undo Closed Tabs with the default value if you want to re-use that feature.
You can temporarily set the pref browser.sessionstore.max_windows_undo to 0 to reset the Recently Closed Windows list,
However there appears to be always one window left that is only removed if you close and restart Firefox.
You can avoid that by closing all tabs before closing the window with only an empty tab left.
Set the pref browser.tabs.closeWindowWithLastTab to false on the about:config page to prevent closing the last tab from closing the browser.